William Peirson

Aqueous surface layer flows induced by microscale breaking wind waves

Publisher: Cambridge University Press (CUP)

Date: 25-03-2003

DOI: 10.1017/S0022112002003336

Application of LiDAR technology for measurement of time-varying free-surface profiles in a laboratory wave flume

Publisher: Elsevier BV

Date: 10-2012

DOI: 10.1016/J.COASTALENG.2012.04.006

Placed Rock as Protection against Erosion by Flow down Steep Slopes

Publisher: American Society of Civil Engineers (ASCE)

Date: 09-2008

DOI: 10.1061/(ASCE)0733-9429(2008)134:9(1370)

Piping fish over dams

Publisher: Elsevier BV

Date: 11-2021

DOI: 10.1016/J.JHER.2021.07.002

Managing Adaptation of Urban Water Systems in a Changing Climate

Publisher: Springer Science and Business Media LLC

Date: 08-03-2012

DOI: 10.1007/S11269-012-0002-8

Evaporation mitigation using floating modular devices

Publisher: Elsevier BV

Date: 11-2015

DOI: 10.1016/J.JHYDROL.2015.10.027

Wave breaking onset and strength for two-dimensional deep-water wave groups

Publisher: Cambridge University Press (CUP)

Date: 07-08-2007

DOI: 10.1017/S0022112007006568

Abstract: The numerical study of J. Song & M. L. Banner ( J. Phys. Oceanogr. vol. 32, 2002, p. 254) proposed a generic threshold parameter for predicting the onset of breaking within two-dimensional groups of deep-water gravity waves. Their parameter provides a non-dimensional measure of the wave energy convergence rate and geometrical steepening at the maximum of an evolving nonlinear wave group. They also suggested that this parameter might control the strength of breaking events. The present paper presents the results of a detailed laboratory observational study aimed at validating their proposals. For the breaking onset phase of this study, wave potential energy was measured at successive local envelope maxima of nonlinear deep-water wave groups propagating along a laboratory wave tank. These local maxima correspond alternately to wave group geometries with the group maximum occurring at an extreme carrier wave crest elevation, followed by an extreme carrier wave trough depression. As the nonlinearity increases, these crest and trough maxima can have markedly different local energy densities owing to the strong crest–trough asymmetry. The local total energy density was reconstituted from the potential energy measurements, and made dimensionless using the square of the local (carrier wave) wavenumber. A mean non-dimensional growth rate reflecting the rate of focusing of wave energy at the envelope maximum was obtained by smoothing the local fluctuations. For the cases of idealized nonlinear wave groups investigated, the observations confirmed the evolutionary trends of the modelling results of Song & Banner (2002) with regard to predicting breaking onset. The measurements confirmed the proposed common breaking threshold growth rate of 0.0014±0.0001, as well as the predicted key evolution times: the time taken to reach the energy maximum for recurrence cases and the time to reach the breaking threshold and then breaking onset, for breaking cases. After the initiation and subsequent cessation of breaking, the measured wave packet mean energy losses and loss rates associated with breaking produced an unexpected finding: the post-breaking mean wave energy did not decrease to the mean energy level corresponding to maximum recurrence, but remained significantly higher. Therefore, pre-breaking absolute wave energy or mean steepness do not appear to be the most fundamental determinants of post-breaking wave packet energy density. However, the dependence of the fractional breaking energy loss of wave packets on the parametric growth rate just before breaking onset proposed by Song & Banner (2002) was found to provide a plausible collapse to our laboratory data sets, within the experimental uncertainties. Further, when the results for the energy loss rate per unit width of breaking front were expressed in terms of a breaker strength parameter b multiplying the fifth power of the wave speed, it is found that b was also strongly correlated with the parametric growth rate just before breaking. Measured values of b obtained in this investigation ranged systematically from 8 × 10 −5 to 1.2 × 10 −3 . These are comparable with open ocean estimates reported in recent field studies.

On the threshold for wave breaking of two-dimensional deep water wave groups in the absence and presence of wind

Publisher: Cambridge University Press (CUP)

Date: 15-12-2016

DOI: 10.1017/JFM.2016.776

Abstract: The threshold for the onset of breaking proposed by Barthelemy et al. ( arXiv:1508.06002v1 , 2015) has been investigated in the laboratory for unidirectional wave groups in deep water and extended to include different classes of wave groups and moderate wind forcing. Thermal image velocimetry was used to compare measurements of the wave crest point (maximum elevation and also the point of maximum) surface water particle velocity ( $U_{s}$ ) with the wave crest point speed ( $C$ ) determined by an array of closely spaced wave gauges. The crest point surface energy flux ratio $B_{x}=U_{s}/C$ that distinguishes maximum recurrence from marginal breaking was found to be $0.840\\pm 0.016$ . Increasing wind forcing from zero to $U_{\\unicode[STIX]{x1D706}/4}/C_{0}=1.42$ systematically increased this threshold by 2 %. Increasing the spectral bandwidth (decreasing the Benjamin–Feir index from 0.39 to 0.31) systematically reduced the threshold by 1.5 %.

Optimising dissolved air flotation/filtration treatment of algae-laden lagoon effluent using surface charge: A Bolivar treatment plant case study

Publisher: IWA Publishing

Date: 10-2012

DOI: 10.2166/WST.2012.373

Abstract: Dissolved air flotation (DAF) incorporating filtration (DAFF) is used at the Bolivar wastewater treatment plant (WWTP) to polish lagoon effluent for reuse. Elevated algal populations are frequently experienced and can lead to increased coagulant requirements and process control issues. Streaming current detectors (SCDs) and a charge demand analyser (CDA) were used to monitor the full-scale plant. This was followed by an optimisation study using a pilot plant with a CDA. It was found that the normal operational charge demand range for DAF at Bolivar was between −46 and −40 μeq L−1. Decreasing the pH of coagulation reduced coagulant consumption and facilitated more sensitive CDA responses to changes in alum dose.

Development of thermal image velocimetry techniques to measure the water surface velocity

Publisher: IOP Publishing

Date: 05-2016

DOI: 10.1088/1755-1315/35/1/012021

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation

Publisher: Elsevier BV

Date: 09-2014

DOI: 10.1016/J.WATRES.2014.05.032

Abstract: Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed. Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer containing the largest hydrophobic functionality resulted in highly anionic treated effluent, suggesting stronger adherence of polymers to bubble surfaces and reduced residual polymer concentrations.

Effect of inflow conditions on the free-surface properties of hydraulic jumps

Publisher: Informa UK Limited

Date: 09-04-2021

DOI: 10.1080/00221686.2020.1866692

Municipal gravity sewers: An unrecognised source of nitrous oxide

Publisher: Elsevier BV

Date: 2014

DOI: 10.1016/J.SCITOTENV.2013.08.051

Abstract: Nitrous oxide (N2O) is a primary ozone-depleting substance and powerful greenhouse gas. N2O emissions from secondary-level wastewater treatment processes are relatively well understood as a result of intensive international research effort in recent times, yet little information exists to date on the role of sewers in wastewater management chain N2O dynamics. Here we provide the first detailed assessment of N2O levels in the untreated influent (i.e. sewer network effluent) of three large Australian metropolitan wastewater treatment plants. Contrary to current international (IPCC) guidance, results show gravity sewers to be a likely source of N2O. Results from the monitoring program revealed hydraulic flow rate as a strong driver for N2O generation in gravity sewers, with microbial processes (nitrification and possibly denitrification) implicated as the main processes responsible for its production. Results were also used to develop a presumptive emission factor for N2O in the context of municipal gravity sewers. Considering the discrepancy with current IPCC Guidelines, further work is warranted to assess the scale and dynamics of N2O production in sewers elsewhere.

Nitrous oxide monitoring for nitrifying activated sludge aeration control: A simulation study

Publisher: Wiley

Date: 09-2008

DOI: 10.1002/BIT.21880

Abstract: An activated sludge aeration control concept was developed utilizing off-gas nitrous oxide concentrations as a surrogate for autotrophic nitrifying bacterial inhibition and aeration air as a master control variable. The control concept was evaluated using a simulated pilot scale bioreactor (mathematically calibrated liquid phase process model and a model to link off-gas nitrous oxide generation to liquid phase conditions) as a data generator. When applied to the simulated system, the process controller was successful at maintaining the process at the desired operating setpoint and promoting stable operation by minimizing periods of significant inhibition. Furthermore, it provided a more efficient use of the air supplied to the bioreactor during periods of varying feed loading by matching the air supply to the metabolic demands, substantially reducing periods of over and under-aeration. The findings of this research demonstrate the potential for off-gas nitrous oxide monitoring as a completely non-invasive alternative to liquid phase monitoring used in conventional dissolved oxygen control. Investigations are currently underway at the laboratory scale to evaluate the benefits and limitations associated with this control concept, with particular emphasis on implementation issues and the quantification of potential aeration and cost savings.

The influence of geological conditions on erosion of unlined spillways in rock

Publisher: Geological Society of London

Date: 19-03-2018

DOI: 10.1144/QJEGH2017-087

Linking Reduced Breaking Crest Speeds to Unsteady Nonlinear Water Wave Group Behavior

Publisher: American Physical Society (APS)

Date: 19-03-2014

DOI: 10.1103/PHYSREVLETT.112.114502

Marine nitrous oxide emissions: An unknown liability for the international water sector

Publisher: Elsevier BV

Date: 11-2013

DOI: 10.1016/J.ENVSCI.2013.06.003

On the microphysical behaviour of wind-forced water surfaces and consequent re-aeration

Publisher: Cambridge University Press (CUP)

Date: 05-03-2014

DOI: 10.1017/JFM.2013.681

Abstract: A detailed laboratory investigation of the mechanical and low-solubility gas coupling between wind and water has been undertaken using a suite of microphysical measurement techniques. Under a variety of wind conditions and in the presence and absence of mechanically generated short waves, approximately fetch-independent surface conditions have been achieved over short laboratory fetches of several metres. The mechanical coupling of the surface is found to be consistent with Banner ( J. Fluid Mech. vol. 211, 1990, pp. 463–495) and Banner & Peirson ( J. Fluid Mech. vol. 364, 1998, pp. 115–145). Bulk observations of re-aeration are consistent with previous laboratory studies. The surface kinematical behaviour is in accordance with the observations of Peirson & Banner ( J. Fluid Mech. vol. 479, 2003, pp. 1–38). Also, their predictions of a strong enhancement of low-solubility gas flux at the onset of microscale breaking is confirmed and direct observations show a concomitant onset of very thin aqueous diffusion sublayers. It is found that the development of strong parasitic capillary waves towards the incipient breaking limit does not noticeably enhance constituent transfer. Across the broad range of conditions investigated during this study, the local instantaneous constituent transfer rate remains approximately log-normally distributed with an approximately constant standard deviation of $0.62\\pm 0.15({\\mathrm{log}}_e(\\mathrm{m}~ {\\mathrm{s}}^{-1}))$ . Although wind-forced water surfaces are shown to be punctuated by intense tangential stresses and local surface convergence, localized surface convergence does not appear to be the single critical factor determining exchange rate. Larger-scale orbital wave straining is found to be a significant constituent transfer process in contrast to Witting ( J. Fluid Mech. vol. 50, 1971, pp. 321–334) findings for heat fluxes, but the measured effects are consistent with his model. By comparing transfer rates in the presence and absence of microscale breaking, low-solubility gas transfer was decomposed into its turbulent/capillary ripple, gravity-wave-related and microscale breaking contributions. It was found that an efficiency factor of approximately $17\\, \\%$ needs to be applied to Peirson & Banner’s model, which is extended to field conditions. Although bulk thermal effects were observed and thermal diffusion layers are presumed thicker than their mass diffusion counterparts, significant thermal influences were not observed in the results.

Turbulence beneath finite amplitude water waves

Publisher: Springer Science and Business Media LLC

Date: 04-01-2012

DOI: 10.1007/S00348-011-1254-4

Measurements of the time-varying free-surface profile across the swash zone obtained using an industrial LIDAR

Publisher: Elsevier BV

Date: 11-2010

DOI: 10.1016/J.COASTALENG.2010.07.001

An overview of numerical modelling of the Sydney deepwater outfall plumes

Publisher: Elsevier BV

Date: 1996

DOI: 10.1016/S0025-326X(97)00077-5

Rain-induced attenuation of deep-water waves

Publisher: Cambridge University Press (CUP)

Date: 29-04-2013

DOI: 10.1017/JFM.2013.87

Abstract: A laboratory investigation has been undertaken to quantify water wave attenuation rates as a function of rainfall rate. Vertical artificial rainfall is shown to generate weak near-surface velocity fluctuations that decline systematically away from the free surface and are independent of rainfall rate across the range of rainfall rates investigated (40– $170~\\mathrm{mm} ~{\\mathrm{h} }^{- 1} $ ). In the absence of rain, the observed attenuation of gravity waves is at levels consistent with classical viscous theory, but with a systematic finite- litude effect observed above a mean steepness of 0.10. Wave attenuation rates were found to be independent of the mean wave steepness and identical when artificial rainfall rates of 108 and $141~\\mathrm{mm} ~{\\mathrm{h} }^{- 1} $ were applied. Reassessment of complementary theoretical and experimental studies of in idual droplets impacting on undisturbed water surfaces indicates that above a weak threshold rainfall rate of $30~\\mathrm{mm} ~{\\mathrm{h} }^{- 1} $ , the surface irradiation becomes so frequent that droplet-generated violent surface motions directly interact with the incoming droplets. Present evidence is that a matching of time scales develops between the incoming surface irradiation and surface water motions generated by antecedent droplets as the rainfall rate increases. Consequently, at high rainfall rates, a highly dissipative surface regime is created that transmits little of the incident rainfall kinetic energy to the aqueous layers below. Rainfall-induced wave attenuation rates are compared with measurements of other wave attenuation processes to obtain a hierarchy of strength in both the laboratory and the field. Comparison is also made with wave attenuation theories that incorporate momentum and energy flux considerations. Rain-induced wave attenuation rates are weak or very strong depending on whether they are expressed in terms of energy scaling obtained from above or below the surface respectively, due to the high dissipation rate that occurs in the vicinity of the interface.

Discovery Projects - Grant ID: DP120101701

Start Date: 07-2012

End Date: 04-2017

Amount: $360,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0985602

Start Date: 10-2009

End Date: 12-2012

Amount: $380,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0990189

Start Date: 01-2010

End Date: 12-2014

Amount: $390,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0452505

Start Date: 2004

End Date: 12-2007

Amount: $196,270.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP110100389

Start Date: 11-2011

End Date: 12-2015

Amount: $480,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP1095722

Start Date: 02-2010

End Date: 01-2013

Amount: $320,000.00

Funder: Australian Research Council